Fermentative hydrogen production using various biomass-based materials as feedstock

Hydrogen can be produced through different methods. Various biomass can be used as low-cost substrate for fermentative hydrogen production, which significantly reduces the hydrogen production cost. Furthermore, biohydrogen production from biomass wastes can achieve dual benefits of clean energy generation and waste management since agricultural and municipal wastes can be disposed at the same time. However, the application of hydrogen production from biomass meets the bottlenecks of low hydrogen production rate and substrate degradation rate. In this paper, various biomass as feedstock, including waste activated sludge produced form wastewater treatment plant, algae, agricultural residuals and municipal wastes used for biological hydrogen production, was reviewed. Since the hydrolysis to smaller molecules is the rate-limiting step for biomass degradation, a pretreatment step can enhance both the hydrogen production efficiency and biomass degradation rate. Pretreatment process can destroy the crystal structure of macromolecular substances and reduce their polymerization degree. Therefore the trapped components can be released through cell wall lysis and delignification of lignocellulosic biomass to make higher proportion of readily fermentable substances accessible for microorganisms. Various pretreatment methods used for treating biomass as feedstock for hydrogen production were analyzed and compared. Physical treatment, chemical treatment, biological treatment and a combination of different treatments are usually used for the pretreatment of biomass. Physical treatment methods include mill, grind, ultra-sonication, heat, freeze and thaw, microwave and ionizing radiation; chemical treatment methods comprise acid and alkaline treatment, oxidation by oxidizing agent and addition of methanogenic inhibitors; biological treatment methods mainly consist of enzymatic treatment and bacterial hydrolysis. Pretreatment is a critical process for fermentative hydrogen production from biomass. Considerable efforts are needed from both technical and managing aspects to achieve a full-scale application of fermentative hydrogen production from biomass.